The invention relates to a device for the pre-folding of a closure on a folding box which is rectangular in cross section, and especially oblong-rectangular, at least in the area of the closure, the said closure formed from the creased but unslotted end portion of the walls of the said box, two confronting closure panels being each provided with a pair of creases running from the corners and converging towards the center of the margin for the formation by folding of triangular pockets, the said device consisting of two pairs of folding tools which are placed at 90.degree. to one another, the first pair of which, associated with the end panels provided with converging creases, being movable toward or away from one another, and the other pair being movable toward one another, the said device consisting also of a plunger disposed in the center between the folding tools and adapted to the free cross section of the box, which plunger serves as a backing means in the prefolding of the closure by the folding tools.
The pre-folding of a closure of an unfilled box serves to facilitate the later sealing of the filled box, because even with folding creases the top of the box cannot be perfectly folded and sealed when the box is full. To obviate these difficulties, it is common to pre-fold the end of the box which is provided with folding creases.
In one known device of the kind described above, the folding tools act exclusively externally on the top portion of the box. The folding tools associated with the top panels from which the triangular pockets are made are constructed as substantially triangular plates matching the pockets, while the other two folding tools are in the form of oblong rectangular blocks. With such a device a pre-folding can be achieved which is sufficient for the final folding that comes later on. However, it is disadvantageous that the end portion of the box remains more or less in the pre-folded condition after the pre-folding. This interferes with the further processing of the box, because the plunger cannot be withdrawn from the box unless the box is held. It then scrapes the inside surface of the box, which is coated with a thermoplastic material as an adhesive for the closure.